Cytosolic free calcium and DNA synthesis in BALB/c 3T3 cells: aequorin luminescence studies.

In order to investigate how growth factors stimulate DNA synthesis, we studied the relationship between early increases in the intracellular concentration of free calcium (Cai) and early mitogenic events (competence) in quiescent BALB/c 3T3 cells. Cai was measured by aequorin luminescence, and DNA synthesis was quantitated by autoradiography. While both serum (2%) and platelet-derived growth factor (2 U/ml) stimulated large increases in Cai without inducing competence, fibroblast growth factor (100-400 ng/ml) produced a large number of competent cells without causing a detectable increase in Cai. Thus, there was no correlation between the magnitude of Cai increase and subsequent competence for DNA synthesis.